Experimental Transmission of Sarcocystis muris (Apicomplexa: Sarcocystidae) Sporocysts from a Naturally Infected Cat (Felis catus) to Immunocompetent and Immunocompromised Mice

Cats serve as definitive hosts for zoonotic Toxoplasma gondii, a protozoan that threatens human reproductive health, but they also excrete sporocysts of related protozoan that pose no known human health risk. Here we provide the first definitive evidence for natural infection with the enzootic parasite Sarcocystis muris, one such enzootic parasite. Sporulated Sarcocystis sp. sporocysts were found in rectal contents of an adult feral cat (Felis catus) in Giza, Egypt. After these sporocysts were orally inoculated into 2 Swiss Webster mice, sarcocysts were found to have developed in skeletal muscles 114 days later. As observed through transmission electron microscopy, the cyst wall corresponded to Type 1, and the parasitophorous vacuolar membrane had tiny outpocketing of blebs (